1. Technical Field
The present invention relates to pneumatic devices, and particularly to an improved pneumatic device with simple construction, small volume and a novel air channel and without loss of efficiency.
2. Description of Related Art
The environmental protection concepts and corresponding practical actions have been practiced for many years. Correspondingly, energy resources have evolved from the early forms of steam power, thermal power and hydropower to the modern forms of electric power, solar energy and pneumatic power which feature higher efficiency. All of these energy source forms reveal that, with rapid development of the science and technology, it is possible to use different energy sources or composite energy sources for various appropriate purposes. However, some energy sources cannot be obtained without a lot of cost or without damage to the ecosystem on the earth (e.g., the nuclear energy and the thermal power), so they are only restricted to use in some large-scale industrial purposes or general life sectors; on the other hand, other energy sources unsuitable for use by many users on a large scale (e.g., solar energy and pneumatic power) are widely used by single users or a few collective users.
A typical energy source that is widely used by single users or a few collective users in recent years is the pneumatic power. Pneumatic tools are known as one application of the pneumatic power. Examples of the pneumatic tools include pneumatic wrenches for detaching nuts of tires, pneumatic nail guns, pneumatic glue applicators and the like. These are all inexpensive and highly efficient pneumatic energy sources that are suitable for use by single users in daily life. In order to make efficient use of these cheap energy sources, the tools by means of which the pneumatic sources are applied become very important.
Furthermore, because of the economic depression, a lot of small works in families are now mostly carried out by family members themselves in order to eliminate the high expense of employing professionals. This is especially the case in America which is affected the most by the Financial Tsunami in recent years. The labor cost of employing professionals in America is relatively high, so for simple works, it is naturally the best choice for family members to accomplish such works by themselves in a simple and economic way. Of course, use of professional tools, e.g., building a house by using a pneumatic tool, is also undoubtedly a good choice to reduce the cost and increase the efficiency. Taking a case of building a house as an example, a spacing of 16 inches between individual beams is specified in construction specifications in America. Consequently, the length of current nail guns makes it inconvenient and difficult to work with such nail guns between two beams.
Referring to FIG. 16, there is shown a first front view of a movable-cylinder nail gun according to a first prior-art device. The movable-cylinder nail gun includes a gun body 1′; a downwards-movable cylinder 3′ disposed in the gun body 1′; a piston 4′ for firing nails that is disposed in the cylinder 3′; at least two airtight gaskets 41′ and 42′ disposed on the piston 4′ to divide an interior of the cylinder 3′ into a top cylinder chamber 31′ and a bottom cylinder chamber 32′; a main air chamber 10′ formed inside the gun body 1′, which extends between a handle 11′ of the gun body 1′ and a periphery of the cylinder 3′ to collect high-pressure air that is continuously supplied by an external source via a tail end of the handle 11′ at a constant pressure; and a trigger valve 51′ disposed at an end of the main air chamber 10′ to be driven by a trigger 5′ disposed on the gun body 1′ so as to open and close a path between the main air chamber 10′ of the handle 11′ and a trigger air channel 17′ in the gun body 1′.
Referring to FIG. 17, there is shown a second front view of the movable-cylinder nail gun according to the first prior-art device. The cylinder 3′ is formed with a head valve 8′ integrally at a top portion thereof. The head valve 8′ has a main air-valve port 81′ and an airtight ring 82′ disposed thereon, and the gun body 1′ has an annular ribbed wall 12′ therein. Before the cylinder 3′ moves downwards, the airtight ring 82′ can cling closely to the annular ribbed wall 12′ to close a path that communicates between the main air chamber 10′ and the top cylinder chamber 31′ through the main air-valve port 81′; and when the cylinder 3′ moves downwards, the airtight ring 82′ can disengage from the annular ribbed wall 12′ to open the path. Moreover, the head valve 8′ is formed with an annular rib 83′ inside a top portion thereof. The gun body 1′ has, disposed at a top portion thereof, a cushion 84′ and at least one upper air vent 13′ communicating with the outside atmosphere. The annular rib 83′ on the head valve 8′ can open a path between the upper air vent 13′ and the top cylinder chamber 31′ to drain the high-pressure air in the top cylinder chamber 31′ before the cylinder 3′ moves downwards, and abut against the cushion 84′ to close the path when the cylinder 3′ moves downwards.
As can be known from the above description, in the prior-art device as shown in FIG. 17, components on the right side such as the airtight ring 82′, the main air-valve port 81′, the upper air vent 13′, the annular rib 83′ and the head valve 8′ all lead to in increase of the length thereof. This kind of design, plus the aforesaid restriction imposed by current regulations in America, not only restricts operations of users but also increases the manufacturing cost and consequently the price of the product, making the product less competitive in the market.
Furthermore, referring to FIGS. 18 to 20, there are shown a diagram of a fixed-cylinder nail gun according to a second prior-art device, an enlarged diagram of a portion of the fixed-cylinder nail gun according to the second prior-art device, and a diagram of the fixed-cylinder nail gun according to the second prior-art device in a pressurized and air escaping status respectively. As shown in FIG. 18, the fixed-cylinder nail gun mainly has a fixed cylinder 101, a piston 102, a valve housing 103, a main air chamber 104, a top cylinder chamber 105, an exhaust airlock 106 and an air vent 107. The valve housing 103 is disposed around the fixed cylinder 101 to control entry of the high-pressure air from the main air chamber 104 into the top cylinder chamber 105 to push the piston 102 for firing of a nail. Upon completion of firing the nail, i.e., in a return stroke of the piston 102 after firing the nail, the exhaust airlock 106 begins to exhaust the air. As shown in FIG. 19, as the valve housing 103 is closed, the main air chamber 104 and the top cylinder chamber 105 do not communicate with each other, and on the other hand, the exhaust airlock 106 has already been opened; therefore, this represents a status that the air in the top cylinder chamber 105 has been exhausted via the exhaust airlock 106 and the vent 107 when the return stroke of the piston 102 is completed. As shown in FIG. 20, i.e., when the operation shown in FIG. 18 is completed, the main air chamber 104 is filled with high-pressure air anew to force the valve housing 103 to open again so that the air enters into the top cylinder chamber 105 as shown by the dashed line in FIG. 20. However, because of the fast flow velocity of the air and because of the design, opening/closing of the valve housing 103 is partially overlapped in time with closing/opening of the exhaust airlock 106, so when the high-pressure air of the main air chamber 104 enters into the top cylinder chamber 105, a part of the air might escape via a gap W1 in the exhaust airlock 106 that has not been completely closed and via the air vent 107 as shown by the dashed line in FIG. 20, thereby decreasing the efficiency of pushing the piston 102.
For the second prior-art device described above, although the air exhausting structure thereof has been improved and shortened in length, the poor design still results in partial overlap in time between opening/closing of the valve housing and closing/opening of the exhaust airlock, leading to decrease in the efficiency of pushing the piston.
Accordingly, there is an urgent need in the art to design an improved pneumatic device with simple construction and small volume and without loss of efficiency so as to solve the problems confronted by the prior-art devices.